required practicals

Question 1

food tests

Test for reducing sugars

Answer 1

1) Add Benedict’s reagent, mix and heat
2) look for colour change from blue to brick red (positive)

Question 2

food tests

Test for non-reducing sugars

Answer 2

1) Add 2 drops of HCL to solution in test tube
2) Heat in water bath
3) Neutralise with sodium hydroxide solution
4) add Benedict’s solution mix and heat
5)look for colour chamber from blue to brick red (positive)

Question 3

food tests

test for proteins

Answer 3

1) Mix solution with Biuret reagent
2) Purple = positive

Question 4

food tests

test for starch

Answer 4

1) mix solution with potassium-iodine solution
2) colour change to blue/black= positive result

Question 5

food tests

test for fats and oils (lipids)

Answer 5

1) add ethanol and shake
2) add cold water
3) cloudy white emulsion = positive

Question 6

DNA extraction

Answer 6

1) remove calyx from strawbery
2) put strawberry in plastic bag and crush
3) add extraction liquid ( 10cm3 detergent + 1g salt + 100cm3 water) and mix gently
4) filter into beaker
5) pour down side 90% alcohol
6) remove DNA ( cloudy white)
7) Test with acetic-orcein stain - red colour = nucleic acids